1. Technical Field
The present invention relates to an image forming apparatus.
2. Background Art
When an image is formed by an image forming unit disposed in an image forming apparatus, a charger charges a surface of a latent image bearer while cyclically changing a power of the charger, to thereby cyclically change a developing bias to be applied to a developer bearer of a developing device.
For example, the above image forming apparatus forms a latent image on the latent image bearer and develops the latent image while cyclically changing the charging power and the developing bias, to thus form a toner image. Specifically, the image forming apparatus allows an electrostatic latent image formed on the latent image bearer or a photoconductor to be developed by a developer borne on a developing roller, to thereby obtain a toner image. At that time, cyclical variation in the image density caused by variations in the development gap between the photoconductor and the developing roller in accordance with the rotation of the photoconductor due to a distortion in the external surface of the photoconductor is suppressed.
Specifically, the developing bias is cyclically changed based on readings by a rotary encoder as to the rotary attitude of the photoconductor and a predetermined variation pattern of the development. With this structure, the image density variation in a solid portion of the image due to the gap variation can be canceled by the image density variation in the solid portion due to the change in the developing bias, so that the image density variation in the solid portion followed by the rotation of the photoconductor can be suppressed.
That is, based on the detected rotary attitude of the photoconductor and a predetermined charge variation pattern, the charge intensity or strength is cyclically changed by the cyclical change in the charging bias to be applied to the charging member that uniformly charges the surface of the photoconductor. With this structure, occurrence of the cyclic image density variation in a halftone image due to cyclically changing the developing bias can be suppressed.